General Q&A for Class 12 · Page 65
5,215 free answers in General for Class 12 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- GeneralClass 12All
What irrigation system directly draws water from rivers?
The river lift system is an irrigation method that directly draws water from rivers using pumps and motors. This system is particularly useful in areas where the river water level is lower than the agricultural fields. It provides a reliable water source for irrigation in regions with perennial rivers.
- GeneralClass 12All
What are two examples of pesticides?
Two common pesticides are Malathion (an insecticide used to control insects) and 2,4-D (a herbicide used to control broadleaf weeds). Pesticides help protect crops from pests, diseases, and weeds, though they should be used judiciously to minimize environmental impact and health risks.
- GeneralClass 12All
What is the growing season for kharif crops?
The kharif season runs from June to October, coinciding with the monsoon or rainy season. Kharif crops are sown at the beginning of the monsoon and harvested after the rains end. Examples include rice, maize, cotton, and soybeans, which require significant moisture during their growing period.
- GeneralClass 12All
Where are permanent tissues located in a plant?
Permanent tissues are located throughout the plant body, occupying regions beyond the actively dividing meristematic zones. They comprise the bulk of mature plant organs including roots, stems, and leaves. Specifically, the epidermis (outer protective layer), cortex (storage region), vascular bundles (transport system), pith (central storage area), and mesophyll (photosynthetic tissue in leaves) all consist of permanent tissues. These differentiated tissues form the functiona
- GeneralClass 12All
Why is xylem less developed in hydrophytes (aquatic plants)?
In hydrophytes, xylem is less developed because these plants are surrounded by water and don't need extensive water transport systems. Since aquatic plants can absorb water directly through their entire surface area, they don't face the water scarcity challenges that terrestrial plants do. The reduced xylem allows hydrophytes to develop large air spaces (aerenchyma) instead, which provide buoyancy and facilitate oxygen transport to submerged parts. This adaptation demonstrate
- GeneralClass 12All
What is the role of epidermis in plants?
The epidermis serves as the outermost protective layer of plants, forming a barrier against water loss, mechanical injury, pathogen invasion, and environmental stress. Typically consisting of a single layer of tightly packed cells, the epidermis is often covered by a waxy cuticle that minimizes water evaporation. It contains specialized structures like stomata (for gas exchange), trichomes (hair-like structures for protection), and root hairs (for absorption). The epidermis e
- GeneralClass 12All
How are simple tissues different from complex tissues in plants?
. Simple tissues are composed of only one type of cell that performs a single, uniform function—examples include parenchyma, collenchyma, and sclerenchyma. Complex tissues, conversely, contain multiple cell types working together to perform combined functions—xylem and phloem are prime examples. While simple tissues provide support, storage, or photosynthesis through uniform cell action, complex tissues create integrated
- GeneralClass 12All
Where are meristematic tissues located in plants?
Meristematic tissues are found in specific growth regions of plants. Apical meristems are located at the tips of roots and shoots, enabling vertical growth. Lateral meristems (cambium) are positioned along the sides of stems and roots, facilitating thickness increase. Intercalary meristems appear at the base of leaves or internodes, particularly in grasses and monocots. These strategic locations allow plants to grow continuously throughout th
- GeneralClass 12All
What are permanent tissues and how do they differ from meristematic tissues?
Permanent tissues are plant tissues composed of cells that have completed differentiation and ceased dividing. Unlike meristematic tissues, which contain small, actively dividing cells with thin walls and dense cytoplasm, permanent tissues have cells that are larger, specialized for specific functions, and have varying wall thicknesses depending on their role. The key difference lies in their growth activity: meristematic tissues continuously produce new cells, while permanen
- GeneralClass 12All
What is the primary function of meristematic tissues?
The main function of meristematic tissues is to produce new cells through continuous cell division, enabling plant growth and development. These actively dividing cells are responsible for increasing both the length (through apical meristems) and width (through lateral meristems) of plants. Meristematic cells remain in a perpetually active metabolic state, providing the foundation for all other specialized tissues that develop as the plant matures. This growth capacity is ess
- GeneralClass 12All
What is the composition of protoplasm?
Protoplasm is the living substance within a cell, comprising all the material inside the cell membrane. Its composition includes: (1) Water – typically 75-85% of protoplasm, serving as the medium for chemical reactions, (2) Proteins – 10-20%, functioning as enzymes, structural components, and regulatory molecules, (3) Carbohydrates – 2-3%, providing energy and structural support, (4) Lipids – 2-3%, for
- GeneralClass 12All
What are the various types of plastids present in a plant cell?
Plant cells contain three main types of plastids: (1) Chloroplasts – green plastids containing chlorophyll that carry out photosynthesis, converting light energy into chemical energy, (2) Chromoplasts – colored plastids containing pigments like carotenoids that give yellow, orange, or red colors to flowers and fruits, and (3) Leucoplasts – colorless plastids that primarily store nutrients, including amyloplasts (storing star
- GeneralClass 12All
What are chromoplasts?
Chromoplasts are plastids containing colored pigments other than chlorophyll. These pigments include carotenoids (producing yellow, orange, and red colors) that give fruits, flowers, and some roots their distinctive hues. Chromoplasts play important roles in attracting pollinators and seed dispersers, as well as protecting plant tissues from excessive light damage.
- GeneralClass 12All
What is another name for sclereids?
Sclereids are also commonly known as stone cells. These specialized cells are a type of sclerenchyma tissue characterized by their extremely thick, lignified cell walls that provide rigidity and hardness. Sclereids are responsible for the gritty texture in pears and the hard shells of nuts, serving as protective elements that give structural strength to various plant parts.
- GeneralClass 12All
What are the main types of tissues found in plants?
Plants contain two primary categories of tissues: meristematic tissues and permanent tissues. Meristematic tissues are composed of actively dividing cells that enable plant growth, while permanent tissues consist of cells that have stopped dividing and perform specialized functions. Permanent tissues are further divided into simple tissues (parenchyma, collenchyma, and sclerenchyma) and complex tissues (xylem and phloem). This organization allows plants to ef
- GeneralClass 12All
Where is collenchyma tissue located in plants?
Collenchyma tissue is primarily located in the peripheral regions of stems, petioles (leaf stalks), and leaf veins. It typically appears just beneath the epidermis in young, growing plant parts. This strategic positioning allows collenchyma to provide flexible mechanical support to organs that are still elongating, such as young stems and leaves. The tissue is especially abundant in herbaceous plants and in the corners of angular stems, where it reinforces the structure while
- GeneralClass 12All
What is the nature of cell walls in collenchyma cells?
Collenchyma cells possess unevenly thickened cell walls composed primarily of cellulose and pectin. Unlike sclerenchyma, these walls are not lignified, which maintains their flexibility. The thickening occurs at the corners of cells or along certain walls, providing mechanical strength while allowing the cells to remain living and capable of stretching as the plant grows. This unique wall composition enables collenchyma to offer both support and flexibility, making it ideal f
- GeneralClass 12All
Which simple tissue has non-living cells: parenchyma, collenchyma, or sclerenchyma?
Sclerenchyma is the simple tissue that consists of non-living cells at maturity. While parenchyma and collenchyma tissues contain living cells with active cytoplasm, sclerenchyma cells die after they develop thick, lignified cell walls. This death is functional—the rigid, empty cell walls provide maximum mechanical support and protection without requiring metabolic maintenance. The lignified walls make sclerenchyma extremely durable, which is why this tissue is used in
- GeneralClass 12All
What is the main function of sclerenchyma tissue?
The primary function of sclerenchyma tissue is to provide mechanical support and strength to plant parts. Composed of cells with heavily lignified, thick walls, sclerenchyma acts as the plant's structural reinforcement, offering rigidity to mature regions that no longer need to grow. This tissue helps plants maintain their shape, resist physical stress, and protect delicate internal structures. Sclerenchyma is found in parts requiring maximum strength, such as seed coats, nut
- GeneralClass 12All
Which simple tissue is used for making ropes?
Sclerenchyma fibers are the plant tissue used for making ropes. These long, slender cells have thick, lignified walls that provide exceptional tensile strength and durability. Commercially important fiber sources include jute, hemp, flax, and coir (coconut fiber). The natural strength and flexibility of sclerenchyma fibers make them ideal not only for rope production but also for manufacturing textiles, sacks, paper, and various industrial materials. The dead, hollow nature o